Filter cake detector



Aug. 28, 1962 R. c. @ESSE 3,050,858

FILTER CAKE DETECTOR Filed Sept. 8, 1959 2 Sheets-Skaail 1 lllllll llll ATTORNEYS R. C. GIESSE Aug. 28, 1962 FILTER CAKE DETECTOR Filed sep'- 8 1959 2 Sheets-Sheet 2 HHH kk 32 INVENTOR E' foar-4r@ @f1-'555 BY 7) M 7% S M ATTORNEYS 3,653,858 v FILTER CAKE DETECTOR Robert C. Giesse, Betten-dorf, lor-7a, assigner to Ametek, Inc., a corporation of Delaware Filed Sept. 8, 195%, Ser. No. 838,496 14 Claims. (5l. Sii-16S) The present invention relates to detectors and particularly to a new and improved filter cake spacing detector.

Industrial filtering apparatus generally employs a plurality of parallel, spaced ltering elements which require periodic cleaning of the lter cake accumulated on the filtering media between adjacent elements, and the eficiency of such apparatus may be greatly impaired if such cake is not removed when the spacing between adjacent cakes has attained a predetermined dimension. lf cake build-up becomes excessive and the cake from adjacent leaves should bridge over, the unbalanced pressures frequently cause distortion or destruction of the leaves.

Devices have been developed for detecting the thickness of cake by the differential in pressure between the prefilt and thatv slightly within the cake of solids that collects on the filtering media, While such devices have met with a degree of success, they are indicative of only the thickness of the cake and do not detect the spacing of the cakes .adjacent filtering elements which is a more direct measure of the filtering cycle limitation. For eX- ample, the thickness of cake on adjacent elements may build up at different rates so that the thickness being measured on one element may not be indicative that the cakes on all elements should be removed or that bridging is occurring.

An important object of this invention is to provide a detector capable of detecting a predetermined spacing of filter cakes on adjacent filtering elements.

Another object of the invention is to provide such a detector in which the pressure of the preiilt is utilized to cause the detector to function.

Another object of the invention is to provide a unitary, self-contained instrument that may be suspended between adjacent elements of a multi-element filtering apparatus and may be capable of detecting when the spacing between adjacent filter cakes has attained a predetermined value.

Another object of the invention is to provide such a detector which can be utilized between any two adjacent filtering elements alone, or between every pair of adjacent elements either in series or in parallel arrangement.

ln one aspect of the invention, a hollow frame member, having a thickness equal to the permissible minimum spacing of filter cake on adjacent filter elements, may include an opening in each side, and one side may be removable for facilitating assembly. Each opening may be closed by an hermetically sealed diaphragm of electrically conducting material, in the center of each of which may be located anl electrical contact.

ln another aspect of the invention, a flexible, hollow tube may be connected to the hollow frame member and its free end may be scaled off. The chamber formed by the diaphragm-closed frame member in communication with the interior of the fiexible, hollow tube may be lled with .a high dielectric so that no short circuiting between the diaphragms will occur when they are connected in series into an electrical circuit except through the contacts at the center of each when they are in engagement.

ln still another aspect of the invention, separate conductors may lead from the separate diaphragms to separate female jack retainers into which male jacks may be plugged that lead from a magnetic relay or the like and a current supply. The construction and arrange- Eh 'Patented Aug. 28, 1962 ment may be such that the two diaphragms are in series with each other and the magnetic relay, so that normally 'the contacts at the center of the diaphragms maintain a magnetic relay energized that holds open a circuit for stopping the filtering cycle, sounding an alarm, initiating a cake-removal cycle or just causing an indicator to indicate a condition requiring cake removal.

With the device suspended between adjacent filterin elements, the normal pressure of the prefilt acts upon both diaphragms as well as upon the flexible tube depending frorn the hollow framemernber in which the diaphragms are mounted. Thisy pressure may be in the order of about 65 psi. and the pressure drop through the cake may be in the neighborhood of as much as 45 p.s.i. The area or" the diaphragms is such that the prelilt pressure acting on them maintains their central contacts closed and the dielectric in the chamber and tube under such pressure that the tube will not be collapsed by the prelilt pressure acting on it.

However', when both diaphragrns are sealed off from the prelilt pressure by filter cakes building up on adjacent elements to a point where the cakes contact the sides of the hollow frame member supporting the diaphragms, the prefilt pressure on the flexible tube collapses it, causing a displacement of the dielectric from the tube into the chamber within the hollow frame member, forcing the diaphragms apart and consequently forcing the contacts at the centers thereof apart. Accordingly,` the magnetic relay is fle-energized, causing stopping of the filtering cycle, sounding an alarm or initiating a cake-removing cycle. v

The above, other objects and novel features of the invention will become apparent from the following specilication and accompanying drawings which are merely exemplary.

ln the drawings:

FIG. l is a partial sectional elevational view of an industrial filter to which the principles of the invention have been applied;

FlGS. 2, 3 and 4 are sectional views of a detail of the spacing indicator in three conditions of cake accumulation on adjacent filtering elements;

FlG. 5 is an enlarged sectional elevational view taken substantially along lines 5 5 of FIG. l; and

FIG. 6 is a sectional elevational view taken substantially along line 6-6 of FIG. 5.

Referring to the drawings, a-nd particularly to FIG. l, the instrument involving the principles of the invention is shown as employed in a vertical pressure-leaf filter comprising a tank l0 that is closed by a removable dome 1l. An inlet pipe l2 is adapted to feed prefilt into the tank Ilf3 u-nder a predetermined pressure. A plurality of leaf-type filters 13 may Ibe mounted in spaced parallel relation, and each may have its outlet 14 connected to a main outlet line d5 that feeds the filtrate from the tank to storage or to a process requiring the filtrate.

The leaf-type filters may comprise rigid, relatively coarse mesh screen 16 surrounded by a hollow frame member i7' having an outlet d4 leading to the main outlet header l5'. rey may be covered with filter cloth that may be treated with filter-aids in a known manner.

Referring to FlGS. 5 and 6, the filter cake spacing Iindicator may be in the form of a pendent which is adapted to be disposed between )the leaf filters. The indicator may include a frame member 1S having a recess 19 therein and provided with a threaded opening 2li on one side thereof. The side o-f frame i8 opposite that containing the threaded opening 2li may include an opening 2l having bars Z2 and 23 ther-eacross. A `diaphragm 24 may be herrnet-ically sealed to the inner wall of member i8 in a manner to close the opening 2l.

A threaded disc 25 may also be provided with a-n openthrough is interrupted.

3 Y ing 26 similar to'the opening 21, and it may also have a diaphragm-27 hermetically sealed `to its one face'. The construction and arrangement may besuch that when disc 25 is threaded into the threaded opening 20 against a gasket 2S, a chamber -is formed by the recess 19 and the disc 25. A fitting 29may connect an outlet 30 `from chamber i9 to another chamber, which inthe embodiment disclosed is shown as a flexible tube 31 having its free end 32 sealed. Each of the diaphgrams 24VV and 27 preferably is made of electrically conducting material coated with an insulating material, and they are connected, respectively, to separate electrical conductors 33 and 34. The conductors 33 and 34 extend throughfpassages within fra-me member 18 and a terminallblock 35 that is threaded into a threaded recess 36 within member 18. The passages through which conductors 33 and 34 pass .are otherwise herrnetically sealed, so that-the chamber formed by recess 19 and the inside of the tube 31 define an hermetically sealed enclosure for a -purpose to lbe described later.

A tubular supporting element 37 may be fixed to the terminal Iblock 35 by a cap 38 that is threaded to the block 35. therein leading from the lterminal lblock 35 to a `female end jack retainer `41. A rnale end jack retainer 42 may be connected to aV conduit k43 by a seat element 44, and a coupling member 45 maybe employed to retain the male jacks -in electrical contact within the female jacks. A cable 45 containing the lines leading from the male jacks extends 'through the tubular member'43 lto the apparatus in sexi-es with a power vsupplyfor controlling the filtering process by stopping it, by operating an al-arm, by initiating a cake-removal cycle or the like, when the circuit there- Referring to FIG. V6, electrical contacts 47 and 4S may `be provided on the facing sides of the electrically conducting `diaphragms 24 and 27, which contacts normally are maintained in engagement.- i

VReferring to FIG. 5, the frame 18 tmayinclude a'closure -49 for an inlet 50 leading to the chamber formed by sure, passing the leaf filters .13 to the outlet 15, thence to a -storage ltank `or to a process requiring the filtrate.

Referring to FIG. 2, fit is evident that with no substantial cake on the filter elements 13.the pressure of the prelilt acts on both diaphragms 24 and 27 as well as on the flexible tube 31. The effective area of the diaphragme `Z4 and 27 relatively to that of ytube 31 issuch that under the conditions of FIG. 2, the contacts 47 and 48 remain closed, and tube 31 is retained full of the dielectric liqud. Referring to FIG. 3,V as the'lter cake 51 builds up on `adjacent elements 13 at different'rates, Vand to a point VWhere the opening 26 is closed off while the opening 21 is still open, the pressure of the prelilt forces the diaphragme 24 and 27 rightwardly While still retaining contacts V47 and 48 in engagement. The pressure in opening 26 is less than the prefilt pressure as applied to opening 21 and the flexible Itube 31 lby an amount equalV to the pressure drop across the sealed face of the detector housing18. Any liquid entrapped within the contines 'of openings 26 and the filter cake closing it will be forced through the cake to the interior of the leaf filter. i

Referring to FIG. 4, when Iboth openings 21 and Y26 are closed olf, by the building up of the cake 51, the

Y spacing of the cake 51 yon adjacent filter elements is such as to requireV its removalto insure eicieut filtering of the prelt. The diaphragms 24 and 27 are no longer externally subjected 'to 4the pressure of the prefilt sincethe openings 21 and26 are now lblocked off. However, the

The element 37 may have conductors 39 and 40 em'ble tube 31 is still subjected to the prefilt pressure,V Ycau-,sing it to-collapse and displacing the dielectrictherein into the diaphragm chamber, forcing the diaphragms 24 and 2'7 apart, hence opening contacts 47 and 48. Any liquid trapped within theopenin-g-s 21 and 26 by the cake 51 will be forced 'through the cake, permitting separationv V of the contacts 47 and/48. Separation'of the contacts 47` and 43 de-energizes the circuit leading to the controller for the filtering proces-s. Y,

AlthoughV the various features ofthe filter cake spac-V ing detector have 4been shown and described in detail to fully disclose one embodiment of the invention,Y it will be evident that changes maybe made in such details and certain features may be used without others without n departing from the principles of the invention. Y

What is claimed is: Y i .Y l. A bridging'detector for detecting the spacingbeV tween adjacent surfaces, the spacing between vwhich* varies during the functioning of a process, comprising in combination, interconnected means each havingvoppose'd presmeans while retaining said external pressure Von the pressure responsive means of the other interconnected means.k

2. A bridging detector comprising Vin combination,

liquid filled chamber means; pressure responsive flexible diaphragm means forming opposed walls of part of said chamber means; electrical contact means .responsive vtCt the action of said diaphragm means; pressure responsiveV surface meansY forming `another part Yof said 'chamber means; means effective during a spacing detection to seal olf said diaphragm means in response to a functioninvolving said spacing detectiomrand means responsive Vto said sealing offof said diaphragm means for causing said diaphragm means to operate said contact means. Y

3. A bridging detector for detecting the spacing between adjacent surfaces, the spacing between which varies'during the functioningof a process, comprising in combina` tion, mterconnected fluid actuated Vmeans, each having opposed pressure responsive means disposed between said adjacent surfaces and adaptedrto befexternally subjected to pressure in opposite directions incident to said process;

electrical contact means responsive to the actionof one of said pressure responsive means; and meansVV rendered effective by the variation of the spacing between said adjacent surfaces for removing the external pressure from the pressure responsive means of one of the interconnected means while retaining said external pressure on the pressure respons1ve means of the other' of the interconnected means. Y

4. `In al bridging detector, a sealed chamber comprising parallelwalls spaced apart an amount equal to the spac'-,. ing desired to be detected; separate opposed flexible Ydi- Y Vaphragrn means attached to each of said walls; electrical contacts fixed to the inner surfaces of said diaphragm means; a resilient tube' means communicating with said chamber having its free end sealed and being adapted to be disposed within thers'pacing of said parallel walls;V separate electrical conductors connected to'each of Said contacts and extending outwardly from said chamber; and high dielectric `liquid substantially filling saidchamberY and tube. y p 5. In a bridging detector, a sealed chamber comprising parallel walls spaced apart an amount'equal to the spac? ing desired to be detected, said walls having aligned openings; flexible diaphragm means attached to the inner sur-Y faces of said walls and covering said openings; electrical Y contacts fixed to the inner surfaces of said diaphragm means; a resilient tube communicating with said chamber having its free end sealed and being adapted to be disposed within the spacing of said parallel walls; separate electrical conductors connected to each of said contacts and extending outwardly from said chamber; and dielectric liquid substantially filling said chamber and tube.

6. In a bridging detector, a pressure responsive sealed chamber means comprising parallel walls spaced apart an amount equal to the spacing desired to be detected; separate opposed iiexible diaphragm means attached to each of said walls; electrical contacts fixed to the center of the inner Surfaces of said diaphragm means; another pressure responsive sealed chamber means in communication with said pressure responsive chamber means and having an outside transverse dimension less than that of said pressure responsive chamber means; separate electrical conductors connected to each of said contacts and extending outwardly from said pressure responsive charnber means; and dielectric liquid substantially filling said chambers.

7. In a bridging detector, a pressure responsive sealed chamber means comprising parallel walls spaced apart an amount equal to the spacing desired to be detected said walls having aligned openings; flexible diaphragm means attached to the inner surfaces of said walls and covering said openings; electrical contacts iixed to the center of the inner surfaces of said diaphragm means; another pressure responsive sealed chamber means in communication with said pressurev responsive chamber means and having an outside transverse dimension less than that of said pressure responsive chamber means; separate electrical conductors connected to each of said contacts and extending outwardly from said pressure responsive chamber means; and dielectric liquid substantially filling said chambers.

8. A bridging detector for use with multiple leaf-type filters comprising in combination, a pendant adapted to be supported between adjacent leaf filters; separate interconnected means supported by said pendant, and each having opposed pressure responsive means adapted to be externally subjected to the pressure of the preiilt between said -leaf filters; electrical contact means responsive to the action of one of said pressure responsive means; and means rendered eiective by the lter cake accumulating on the adjacent leaf filters for removing the pretilt pressure from the pressure responsive means of one of said interconnectedY means while retaining the prelt pressure on the pressure responsive means of the other of said interconnected means.

9. A bridging detector for use with multiple leaf-type ilters comprising in combination, a pendant adapted to be supported between adjacent leaf iilters; fluid lled intercommunicating chamber means; opposed pressure responsive means forming part of said chamber means and externally subjected to the pressure of the preiltv between said leaf filters; electrical contact means responsive to the action of the pressure responsive means of one of said chamber means; and means rendered effective by the filter cake accumulating on said adjacent leaf filters for removing the preilt pressure from the pressure responsive means of one of said intercommunicating chamber means while retaining the preiilt pressure on the pressure responsive means of the other of said intercommunicating chamber means.

10. A bridging detector for use with multiple leaf-type filters comprising in combination, a pendant adapted to be supported between adjacent leaf lters; liquid tilled chamber means supported by said pendant; flexible diaphragm means forming opposed walls of part of said chamber means; electrical contact means responsive to 6 v the action of said diaphragm means; pressure responsive surface means forming another part of said chamber means; means responsive to the lter cake accumulating on said adjacent leaf filters for sealing olf said diaphragm means for causing said diaphragm means to operate in a 4manner to actuate said contact means.

Vv1l. A bridging detector for use with multiple leaf-type filters comprising in combination, a pendant adapted to be supported between adjacent leaf filters; liquid iilled intercommunicating chambers attached to said pendant and having pressure responsive surface means forming a part thereof; means forming a rigid surface completely surrounding the pressure responsive surface means of one of said chambers and lying within a plane spaced from the pressure responsive surface means of the other of said chambers; and electrical contact means supported by said pendant, said electrical contact means being actuated by the response of the pressure responsive surface means of one of said chambers.

12. A bridging detector for use with multiple leaf-typ nlters comprising in combination, a pendant adapted to be supported between adjacent leaf filters; an hermetically sealed chamber attached to said pendant and comprising parallel walls; separate opposed iiexible diaphragm means attached to each of said walls; electrical contacts fixed to the center of the inner surfaces of said diaphragm means; a resilient tube communicating with said chamber having its free end sealed and having an outside diameter less than the spacing of said parallel walls; separate electrical conductors connected to each of said contacts and extending outwardly from said chamber and through said pendant; and dielectric liquid substantially filling said chamber and tube.

13. A bridging detector for use with multiple leaftype iilters comprising in combination, a pendant adapted to be supported between adjacent leaf filters; an hermetically sealed chamber attached to said pendant and comprising parallel walls, said walls having aligned openings; flexible diaphragm means attached to the inner surfaces of said walls and covering said openings; electrical contacts fixed to the center of the inner surfaces of said diaphragm means; a resilient tube communicating with said chamber having its free end sealed and having an outside diameter less than the spacing of said parallel walls; separate electrical conductors connected to each of said contacts and extending outwardly from said chamber and through said pendant; and dielectric liquid substantially lling said chamber and tube.

14. A bridging detector for use with multiple leaftype filters comprising in combination, a pendant adapted to be supported between adjacent leaf filters; a pressure sensitive hermetically sealed chamber means attached to said pendant and comprising parallel spaced walls; separate opposed exible diaphragm means attached to each of said walls; electrical contacts xed to the center of the inner surfaces of said diaphragm means; another pressure responsive hermetically sealed chamber means in communication with said pressure sensitive hermetically sealed chamber means and having an outside transverse dimension less than that of said pressure sensitive hermetically sealed chamber means; separate electrical conductors connected to each of said contacts and extending outwardly from said pressure sensitive hermetically sealed chamber means and through said pendant; and dielectric liquid substantially lling said chamber means.

Vallez May 29, 1917 Stoltenberg Nov. 10, 1959 

